Number Of Microbial Cells Research Articles

Microbiological hazards associated with the use of water in the post-harvest handling and processing operations of fresh and frozen fruits, vegetables and herbs (ffFVH). Part 2 - A dynamic mass balance model for handling and processing operations in ffFVH using water.

A dynamic mass balance model was developed to simulate contamination dynamics in the process water of fresh and frozen fruits, vegetables and herbs (ffFVH) during processing and handling operations. The mass balance relates to the flux of water and product in a wash tank and the number of microbial cells released in the water, inactivated by the water disinfectant or transferred from the water back to the product. Critical variables describing microbial dynamics in water are: (i) the chemical oxygen demand (COD), as an indicator of the concentration of organic matter; (ii) free chlorine (FC) and particularly its antimicrobial fraction, hypochlorous acid (HOCl); and (iii) the microbial population levels. Model parameters include: (i) the dilution rate of the process water, representing the speed of system saturation, equal to the water flux divided by the tank volume; (ii) the transfer rates of total bacterial counts (TBC) and COD from product to water; and (iii) the specific inactivation rate of microorganisms due to HOCl. The protective effect of COD on microbial cells against FC is encompassed in the inactivation rate. HOCl is expressed as a function of temperature, pH and total chlorine. The model can simulate 'what if scenarios', based on user-defined process-specific and product/microorganism-specific parameters through a web R-based application. This model can help food business operators when selecting intervention strategies and conditions to maintain the microbiological quality of the process water or identify conditions that represent poor or proper water management practices. Testing alternative model structures and collecting data about operational conditions of handling and/or processing operations, microbial dynamics and the magnitude of the product-specific protective effect on microorganisms are recommended to improve the application of the model.

Different dissolved organic matter sources sustain microbial life in a sandy beach subterranean estuary – an incubation study

In subterranean estuaries (STE), fresh and saline groundwater introduce dissolved organic matter (DOM) of different origin. This DOM serves as substrate for microorganisms that thrive in the STE. In high-energy beaches with dynamic porewater advection, microbial communities face frequent changes in groundwater composition, even at several meters depth. It is unknown how DOM from deep STE groundwater (> 5 m depth) is transformed by prevailing microbial communities. To address this question, we performed sediment incubations in flow-through reactors (FTRs) with deep (6 m depth) STE groundwater of low (1.6) and high salinity (29.1). FTR setups were sampled daily for quantification of dissolved organic carbon (DOC), and at start and end (day 13) of the incubation for analysis of DOM composition, microbial cell numbers and community composition. Solid-phase extracted DOM was molecularly characterized via ultrahigh-resolution Fourier-transform ion cyclotron resonance mass spectrometry. Both groundwater types contained mainly reworked DOM. Corroborating its presumed origin, the fresh groundwater had a more terrestrial DOM signature with a higher proportion of aromatic compounds compared to the saline groundwater. Over the course of the incubation, DOC concentrations increased primarily due to leaching of sedimentary organic matter, providing an additional source of DOM. In all setups, the DOM composition changed significantly from start to end, and similarly for fresh and saline groundwater. From the ~2700 molecular formulae (MF) detected on day 0, 34-35% were removed during the incubations, demonstrating the potential of deep STE microbial communities to degrade recalcitrant DOM that is supplied with the advective porewater flow. However, a substantial portion of MF (63-64%) was retained in both groundwater types, indicating that a fraction of deep STE-DOM is resistant to removal. Properties of MF that were newly detected on day 13 (26-28%) were indicative of labile DOM. Some of these newly detected MF were also identified in sediment-leachates, suggesting that beach sediments are a source of fresh DOM for the STE microbial communities. It is likely that due to longer groundwater residence time in the STE, continuous leaching and microbial processing shift the molecular composition of released DOM from more labile to more recalcitrant DOM.

RAPID METHODS FOR DETECTION OF FOODBORNE PATHOGENS AND THEIR TOXINS - A REVIEW OF CURRENT TRENDS AND FUTURE PERSPECTIVES

Background: Food safety is of utmost importance to sustaining life and promoting good health and is a main problem in any country, regardless of economic and social development. Unsafe food containing harmful pathogens and their toxins cause hundreds of diseases, particularly affecting infants, young children, the elderly and sick people. Therefore, the rapid detection of foodborne pathogens is of great significance for public health. The aim of this review was to provide comprehensive information regarding methods for the detection of foodborne pathogens as well as genus Fusarium and their toxins, from fundamental to state-of-the-art, presenting their advantages and limitations in order to update current knowledge. Review Results: The traditional culture-based methods for the detection of pathogens in food are usually laborious, limited by complex sample preparation procedures, time-consuming, slow to provide results, and require well-trained professional staff. However, compared to these methods, the new ones - immunological methods, nucleic acid-based assays and biosensor-based methods are rapid, accurate, highly sensitive and specific, and easy to use. Precisely providing accurate real-time results would help limit foodborne disease outbreaks, ensure compliance with legislation setting maximum levels of pathogens in certain food categories, detect and improve the import of food contaminated with dangerous levels of pathogenic microorganisms, and ensure public health safety. Conclusion: The development of rapid and automated methods that detect real-time, small numbers of viable microbial cells within a given volume of food is vital in the prevention, transmission and treatment of foodborne diseases. Such methods would also offer a great commercial advantage in the food industry and related fields.

Efficiency of using the "Meadow of Health" feed table cover

The results of using the polymer cover of the feed table "Meadow of Health" in comparison with the concrete feed table are presented. The research was carried out in the conditions of the dairy livestock complex of the Kirov region on milk cows of the Black-and-White Holstein breed during the lactation period. Concrete feed tables for cows during the lactation stabilization period at the time of carrying out had average wear, while the cover of the feed table "Meadow of Health" remained smooth and even for 6 months. The study of microbial contamination of feed table covers showed, that already one month after the beginning of the experiment, the number of microbial cells was 54.7% lower (p < 0.05) in the 1st experimental group, where the "Meadow of Health" cover was used, compared to the concrete table. The amount of uneaten feed residues on the feed tables with the "Meadow of Health" cover was less in comparison with the concrete feed table (p < 0.05), which indicates better palatability of forage mixture from this cover. When transferring cows from polymer cover to concrete from the 2nd month of lactation, a decrease in average daily milk yields by 0.9 kg was observed. By the 4th month of lactation, the reduction in milk yield was 4.8 kg of milk per head per day. When transferring cows from a concrete feed table to a polymer one, there was an increase in milk productivity by 0.4–1.3 kg per head/day. In the first 3 months, the consumption of feed from a polymer-coated table increased by 2.3–5.6% compared to the concrete one. During 5 months of lactation, cows from the cover of the feed table "Meadow of Health" ate feed by 6.8–8.6% more than from concrete, which led to greater productivity of the animals during the analyzed period. The use of the polymer cover of the feed table "Meadow of Health" allowed to get additional profit in the amount of 20,460 rubles and recoup the costs of its installation already on the 39th day of use.

Comparative characteristics of physicochemical properties and safety indicators of fermented sunflower press cake and sunflower meal

To compare the effect of biofermentation method on sunflower press cake and sunflower meal, we studied their physicochemical properties and biological and chemical safety indicators under the influence of Lesnov’s ferment. We determined that fermentation was more effective for sunflower meal compared to sunflower press cake - the mass fraction of crude protein, soluble carbohydrates, and the amount of starch increased. This allows us to recommend biofermentation as a suitable way to prepare sunflower meal for animal feed. The number of microbial cells of mold and the number of yeast cells (CFU/g), pesticides, nitrates and nitrites, toxic elements in sunflower press cake and sunflower meal both before and after fermentation were within the normative MAC. Keywords. Sunflower press cake and meal, Lesnov’s ferment, biofermentation, quality, safety.

Metataxonomic analysis of milk microbiota in the bovine subclinical mastitis.

Subclinical mastitis is one of the most widespread diseases affecting dairy herds with detrimental effects on animal health, milk productivity, and quality. Despite its multifactorial nature, the presence of pathogenic bacteria is regarded one of the main drivers of subclinical mastitis, causing a disruption of the homeostasis of the bovine milk microbial community. However, bovine milk microbiota alterations associated with subclinical mastitis still represents a largely unexplored research area. Therefore, the species-level milk microbiota of a total of 75 milk samples, collected from both healthy and subclinical mastitis-affected cows from two different stables, was deeply profiled through an ITS, rather than a traditional, and less informative, 16S rRNA gene microbial profiling. Surprisingly, the present pilot study not only revealed that subclinical mastitis is characterized by a reduced biodiversity of the bovine milk microbiota, but also that this disease does not induce standard alterations of the milk microbial community across stables. In addition, a flow cytometry-based total bacterial cell enumeration highlighted that subclinical mastitis is accompanied by a significant increment in the number of milk microbial cells. Furthermore, the combination of the metagenomic and flow cytometry approaches allowed to identify different potential microbial marker strictly correlated with subclinical mastitis across stables.

Quantitative analysis of protective T cell immunity against brucellosis

The results of study relationship between antigen reactivity of T-lymphocyte population under ex vivo conditions and the intensity of protective post-vaccination immunity to causative agent of brucellosis are presented. Тaking into account the peculiarities of immunopathogenesis brucellosis and prevailing role of adaptive T-cell immunity to protect against the causative agent of infection, possibility predictive evaluation of protective immunity against brucellosis using CAST-tests is considered as the most important aspect of brucellosis problems. There is an obvious need for an ex vivo correlation analysis of the activity of antigen stimulation of T cells and the intensity of protective immunity formed after vaccination. A close direct proportional relationship was established between the number of live microbial cells Brucella abortus 19BA vaccine strain administered and increase in ex vivo CD3-cell activation. A close correlation was revealed between ex vivo value of antigen-induced stimulation CD3-lymphocytes and level of post-vaccination immunological protection against brucellosis infection. It has been shown that in biomodels vaccinated against brucellosis with a T-lymphocyte stimulation coefficient of 50% or more (according to intensity of antigen-induced ex vivo expression CD25), 100% protection from the development of brucellosis infection after infection with Brucella melitensis at a dose of 1 × 103 live microbial cells are provided. At the same time, there was a lack of a close correlation between an increase in the dose of brucella vaccine strain administered to biomodels and a change in geometric mean antibody titer, presence of a weakly pronounced relationship between level of agglutinins and immunological protection of biomodels from development brucellosis infection and indicators bacterial contamination body.Based on results of study, it was demonstrated that it is possible to quantify the formation and protective activity of T-cell immunity to causative agent of brucellosis based on analysis of level antigen reactivity of CD3-lymphocytes ex vivo. The data obtained and described methodological approach can be used as a predictive criterion in assessing protective level of cellular immunity to causative agent of brucellosis in vaccinated or recovering patients, as well as in order to analyze effectiveness of specific prophylaxis brucellosis and study immunogenicity and protective properties candidate for brucellosis vWe present the results of studies related to antigen reactivity of T lymphocyte population under ex vivo conditions and the intensity of protective post-vaccination immunity to causative agent of brucellosis. Due to peculiarities of immunopathogenesis in brucellosis infection and prevailing role of adaptive T cell immunity for protection against the causative agent of infection, a predictive evaluation of protective immunity against brucellosis using CAST-tests is considered the most important issue in the field. There is an obvious need for ex vivo analysis of correlations between the activity of antigen stimulation of T cells, and the intensity of protective immunity raised after vaccination. A close direct relationship was established between the number of live microbial cells of Brucella abortus 19BA vaccine strain administered, and increase in ex vivo CD3 cell activation. A close correlation (r = -0.841 ÷ -0.966, R2 = 0.708 ÷ 0.969) was revealed between ex vivo values of antigeninduced stimulation of CD3 lymphocytes, and the levels of post-vaccination immunological protection against brucellosis infection. We have shown that, in biomodels vaccinated against brucellosis with a T lymphocyte stimulation coefficient of 50% or more (according to intensity of antigen-induced ex vivo CD25 expression), 100% protection against brucellosis infection was achieved after contamination with Brucella melitensis at a dose of 1×103 live microbial cells. At the same time, a lack of a close correlation was noted between an increased dose of Brucella vaccine strain administered to biomodels, and a change in geometric mean of antibody titer (R2 = 0.357÷0.404), along with a weak relationship between the levels of agglutinins and immunological protection of biomodels from developing brucellosis infection and indices of in vivo bacterial contamination.These results suggest an opportunity to quantify development and protective activity of T cell immunity to the causal agent of brucellosis based ex vivo levels of antigen reactivity of CD3 lymphocytes. A correlation analysis between the state of T cell antigen reactivity and immunological resistance to brucellosis infection indicated a high degree of closeness between these indices. The key influence on activity of protective immunity is exerted by the levels of antigen reactivity of T lymphocytes, whereas the quotient of antigenic stimulation in CD3+CD25+ population may be considered the most informative index of immune protective activity. The data obtained and the described methodology may be used as a predictive criterion in assessing protective level of cellular immunity to causative agent of brucellosis in vaccinated or recovering patients, testing the efficiency of specific prophylaxis in brucellosis and studying immunogenicity and protective properties of candidate vaccines against brucellosis.

The ability of Sitophilus oryzae (Coleoptera, Curculionidae) to transmit Mycobacterium bovis: Morphology, cultural biochemical properties of the bacteria

The problem of tuberculosis has been relevant for many years due to active spread of the infection pathogen around the globe, in particular in Ukraine. In this article, we determined the epizootic role of the rice weevil (Sitophilus oryzae (Linnaeus, 1763); Coleoptera, Curculionidae) in the spread of Mycobacterium bovis. We identified the effect of the beetle on properties of the pathogen, particularly the changes in morphology, cultural, biochemical, and biological properties after the bacteria had travelled through the body of the rice weevil. To achieve our objectives, we used the museum 100th passage of the virulent strain of M. bovis. We employed microscopic, cultural, biochemical, biological (infecting the biological model), pathoanatomic, histological methods, and PCR studies. The rice weevil is able to retain mycobacteria and release them into their environment for 30 days after becoming infected, with gradual decrease in the number of microbial cells. According to morphology and cultural properties, the pathogen we isolated in the experiment was identical to the initial culture. Enzymatic activity of the bacteria varied. The bacteria that had passed through the intestines of M. bovis were observed to have changes in the biochemical parameters which helped them to adapt to the new environment. We measured the effect of the rice weevil on pathogenicity of M. bovis, isolated directly from the beetle and from grain contaminated with the insects during the experiment. The practical importance of the study consists in expansion of our understanding of the ways M. bovis spreads, identification of effect the rice weevil has on mycobacteria. It also might help in the search for ways to interrupt the chain of tuberculosis transmission – prevention of spread of the disease to favourable areas.

Endophytic microorganisms of potato (<i>Solanum tuberosum</i> L.): biodiversity, functions and biotechnological potential

Endophytic communities represent a fascinating inner world of the plants. Endophytes are found in all plant species studied, though the number of microbial cells and their species diversity can differ a lot. The potato (Solanum tuberosum L.) is economically important staple food crop, and the induction of plant resistance to various infections as well as the search for the effective eco-friendly preparations could provide higher potato yields and are very promising for modern agriculture. In this review, we focus on the biodiversity of the potato endophytes and the aspects of their functional importance and possible application in the biological control of plant pathogens. We have systematized literature data regarding the prevention of the harmful effect of pathogenic fungi, bacteria, viruses, and insects resulting from the vital activity of the endophytic microorganisms within the potato plants.

A Gut-on-a-Chip Model to Study the Gut Microbiome-Nervous System Axis.

The human body is colonized by at least the same number of microbial cells as it is composed of human cells, and most of these microorganisms are located in the gut. Though the interplay between the gut microbiome and the host has been extensively studied, how the gut microbiome interacts with the enteric nervous system remains largely unknown. To date, a physiologically representative in vitro model to study gut microbiome-nervous system interactions does not exist. To fill this gap, we further developed the human-microbial crosstalk (HuMiX) gut-on-chip model by introducing induced pluripotent stem cell-derived enteric neurons into the device. The resulting model, 'neuroHuMiX', allows for the co-culture of bacterial, epithelial, and neuronal cells across microfluidic channels, separated by semi-permeable membranes. Despite separation of the different cell types, the cells can communicate with each other through soluble factors, simultaneously providing an opportunity to study each cell type separately. This setup allows for first insights into how the gut microbiome affects the enteric neuronal cells. This is a critical first step in studying and understanding the human gut microbiome-nervous system axis.

CARBON MATERIALS FROM WASTE BIOMASS AS ANTI-BACTERIAL AIR FILTERS

Carbon materials from almond shells were developed for the adsorption of microorganisms from air. Samples were processed by means of a one-step process – high-temperature hydro-pyrolysis. Studies were carried out in a wide temperature range of 600-900 °C. As a result, carbonates with predominant micro- and mesopores were obtained. The samples were impregnated with zinc, silver, iron and copper 5% by weight. The obtained samples were characterized by XDR, BET, scanning electron spectroscopy and elemental analysis. The final products are distinguished by a moderate surface and the presence of nanosized metal particles. The antibacterial properties of the activated carbon composites were examined using standard methodology under dynamic contact conditions and Escherichia coli K12 as test microorganism. All tested composite materials exhibit strong antibacterial properties after 48 h of contact with microbial cells. Thus the application of these materials in filtering system will be possible solution for successful reduction of microbial cell number. It is assumed that a similar effect can be achieved in an air environment.

The Extracellular Matrix of Yeasts: A Key Player in the Microbial Biology Change of Paradigm.

Microbes are traditionally regarded as planktonic organisms, individual cells that live independently from each other. Although this is true, microbes in nature mostly live within large multi-species communities forming complex ecosystems. In these communities, microbial cells are held together and organised spatially by an extracellular matrix (ECM). Unlike the ECM from the tissues of higher eukaryotes, microbial ECM, mostly that of yeasts, is still poorly studied. However, microbial biofilms are a serious cause for concern, for being responsible for the development of nosocomial infections by pharmacological drugs-resistant strains of pathogens, or for critically threatening plant health and food security under climate change. Understanding the organization and behaviour of cells in biofilms or other communities is therefore of extreme importance. Within colonies or biofilms, extremely large numbers of individual microbial cells adhere to inert surfaces or living tissues, differentiate, die or multiply and invade adjacent space, often following a 3D architectural programme genetically determined. For all this, cells depend on the production and secretion of ECM, which might, as in higher eukaryotes, actively participate in the regulation of the group behaviour. This work presents an overview of the state-of-the-art on the composition and structure of the ECM produced by yeasts, and the inherent physicochemical properties so often undermined, as well as the available information on its production and delivery pathways.

Sensitive detection of viable salmonella bacteria based on tertiary cascade signal amplification via splintR ligase ligation-PCR amplification-CRISPR/Cas12a cleavage

Several viable Salmonella bacteria are capable of causing severe human diseases and huge economic losses. In this regard, viable Salmonella bacteria detection techniques that can identify small numbers of microbial cells are highly valuable. Here, we present a detection method (referred to as SPC) based on the amplification of tertiary signals using splintR ligase ligation, PCR amplification and CRISPR/Cas12a cleavage. The detection limit of the SPC assay was 6 copies (HilA RNA) and 10CFU (cell). Based on Intracellular HilA RNA detection, this assay can be used to distinguish between viable and dead Salmonella. In addition, it is able to detect multiple serotypes of Salmonella and has been successfully used to detect Salmonella in milk or isolated from farms. Overall, this assay is a promising test for viable pathogens detection and biosafety control.

Lippia origanoides derivatives in vitro evaluation on polymicrobial biofilms: Streptococcus mutans, Lactobacillus rhamnosus and Candida albicans

ObjectiveThis work evaluated the Lippia origanoides derivatives in vitro effect on polymicrobial biofilms of Streptococcus mutans, Lactobacillus rhamnosus and Candida albicans. Additionally, the cytotoxic effect of the oils on human skin keratinocytes (HaCaT) and fibroblasts of the periodontal ligament (FLP) cell lines was evaluated. DesignThe minimum inhibitory concentration, the inhibitory activity on monomicrobial (S. mutans) and polymicrobial biofilm (S. mutans, L. rhamnosus and C. albicans) of L. origanoides four essential oils and terpenes (thymol and carvacrol) were evaluated. The cytotoxic effect of each one of the compounds was measured, and all the tests were compared against chlorhexidine. ResultsAll the evaluated compounds reached an inhibition percentage of S. mutans monomicrobial biofilms formation of 100 % at 600 µg/mL (p < 0.0001). The highest concentration (2 MIC) eradicated 100 % of S. mutans-preformed biofilms after 5 min L. origanoides carvacrol + thymol and thymol chemotypes showed marked reductions in topography, the number of microbial cells and extracellular matrix on polymicrobial biofilm. The cytotoxic effect of the compounds was very similar to chlorhexidine. ConclusionsL. origanoides essential oils have an inhibitory effect on mono and polymicrobial biofilms. The oils present a similar cytotoxic effect to chlorhexidine on HaCaT and FLP cell lines. However, including these compounds in formulations for clinical use is an exciting proposal yet to be investigated.

Abstract IA006: Measuring the microbiome: Improving the predictive power of microbiome analysis in cancer outcomes

Abstract More than 1,000 species of bacteria, archaea, viruses and fungi live in the human gut. Far from being passive passengers, these organisms strongly interact with one another and with their host’s metabolism and immune system. Compelling early experiments have demonstrated associations between the intestinal microbiome composition and obesity, cardiovascular diseases, and certain cancer chemotherapies’ efficacy. Yet teasing apart the mechanisms by which microbes impact host health has been challenging. To accelerate an otherwise challenging, slow and tedious process and to deconstruct mechanisms, we must critically examine our existing “tool kit” for studying the microbiome, and mature our measurement tools to meet these challenges. Our translational laboratory builds and designs observational and interventional clinical cohorts to study. We have also steadfastly worked to develop genomic tools to study strain level dynamics of the microbiome, how microbial genomes change over time and how microbes use hidden “microproteins” to communicate with each other and their human hosts. In this presentation, I will speak about three recent developments in our lab: (1) I will introduce the importance of absolute quantification in microbiome research, and our efforts toward that. This will form the basis of revised estimates of the number of microbial cells in a human body. (2) I will give an overview of a new computational workflow called “Phanta”, which enables simultaneous taxonomic profiling of eukaryotes, bacteria and viruses in a human gut metagenomic sample. (3) I will share unpublished work on how antibiotic exposure negatively impacts cancer outcomes in patients with triple-negative breast cancer. Citation Format: Ami S. Bhatt. Measuring the microbiome: Improving the predictive power of microbiome analysis in cancer outcomes [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr IA006.

Investigation of lactic acid bacterial profiles in commercial rice wine and their effect on metabolites during low-temperature storage

Makgeolli, the traditional Korean rice wine, is generally considered to contain lactic acid bacteria (LAB) despite its bacterial inoculation-free brewing process. The existence of LAB in makgeolli often presents inconsistent trends in microbial profiles and cell numbers. Therefore, to establish LAB-related insights, 94 commercial non-pasteurized products were collected and microbial communities and metabolites were analyzed using 16S rRNA amplicon sequencing and GC–MS, respectively. All samples contained various LAB genera and species, with an average viable cell number of 5.61 log CFU/mL. Overall, 10 LAB genera and 25 LAB species were detected; the most abundant and frequent LAB genus was Lactobacillus. There was no significant change in the LAB composition profile or lactic acid content during low-temperature storage, indicating the presence of LAB did not significantly affect the quality of makgeolli under low-temperature storage conditions. Overall, this study contributes to understand the microbial profile and role of LAB in makgeolli.

Detritus‐hosted methanogenesis sustains the methane paradox in an alpine lake

AbstractAccumulation of methane in oxic waters of lakes and the ocean has been widely reported. Despite the importance for the greenhouse gas budget, mechanistic controls of such “methane paradox” remain elusive. Here, we use a combination of CH4 concentration and isotopic (δ13CCH4, δDH2O and δ18OH2O) measurements, plankton incubations and microbial community assessments to demonstrate the existence of the methane paradox in oxygenated waters of a meromictic lake (Lake Cadagno, Switzerland). Following mass dynamics using water isotopes, we exclude the possibility that the accumulation of CH4 at the thermocline results solely from lateral transport. Interannual variability in the magnitude of the methane paradox (between 0.5 and 5 μmol L−1) is associated to stratification patterns, changes in zooplankton biomass and planktonic detritus accumulation along density gradients, as well as fluctuating microbial cell numbers. The links between hydrodynamic conditions, aggregation of planktonic detritus and its microbiome, as well as the accumulation of CH4 in the water column are further supported by high‐resolution echo‐sounder measurements revealing backscatter maxima at the top of the thermocline, where detritus is effectively trapped, and by oxic incubations showing that CH4 is produced in zooplankton detritus (0.046 nmol L−1 to 0.095 CH4 mg dry mass L−1 d−1). Our results also show that detritus‐hosted methanogenesis is stimulated through the addition of methylphosphonate, suggesting that zooplankton‐associated microbiomes exploit organic phosphorus compounds to release CH4. Understanding the variability of the methane paradox in relation to changing hydrodynamics and plankton communities will be crucial to predict the future role of lakes in the global methane budget.

Modulation of Biofilm Mechanics by DNA Structure and Cell Type.

Deoxyribonucleic acid (DNA) evolved as a tool for storing and transmitting genetic information within cells, but outside the cell, DNA can also serve as "construction material" present in microbial biofilms or various body fluids, such as cystic fibrosis, sputum, and pus. In the present work, we investigate the mechanics of biofilms formed from Pseudomonas aeruginosa Xen 5, Staphylococcus aureus Xen 30, and Candida albicans 1408 using oscillatory shear rheometry at different levels of compression and recreate these mechanics in systems of entangled DNA and cells. The results show that the compression-stiffening and shear-softening effects observed in biofilms can be reproduced in DNA networks with the addition of an appropriate number of microbial cells. Additionally, we observe that these effects are cell-type dependent. We also identify other mechanisms that may significantly impact the viscoelastic behavior of biofilms, such as the compression-stiffening effect of DNA cross-linking by bivalent cations (Mg2+, Ca2+, and Cu2+) and the stiffness-increasing interactions of P. aeruginosa Xen 5 biofilm with Pf1 bacteriophage produced by P. aeruginosa. This work extends the knowledge of biofilm mechanobiology and demonstrates the possibility of modifying biopolymers toward obtaining the desired biophysical properties.

Research Progress on the Application of Human Oral Microbiome in Forensic Individual Identification.

The oral cavity is the second largest microbial bank in humans after the intestinal canal, colonizing a large number of microorganisms including viruses, bacteria, archaea, fungi and protozoa. The great number of microbial cells, good DNA stability, and individual has a unique microbial community, these characteristics make the human microbiome expected to become a new biomarker for forensic individual identification. This article describes the characteristics of human oral microorganisms and microbial molecular markers in detail, analyzes the potential application value of microorganisms in forensic individual identification, and reviews the research progress of human oral microorganisms in forensic individual identification.

Improving methane production from food waste by intermittent agitation: Effect of different agitation frequencies on solubilization, acidogenesis, and methanogenesis

The intermittent agitation system is effective in reducing energy consumption during anaerobic digestion of organic waste. However, insufficient agitation leads to a significant reduction in reactor performance. Therefore, it is necessary to clarify the organic degradation reactions that are limited or accelerated by agitation to ensure proper agitation. This study aimed to investigate the effects of different agitation frequencies on solubilization, acidogenesis, and methanogenesis. Food waste, which is a relatively easily degradable and common substrate for anaerobic digestion, was treated in a mesophilic batch operation under continuous, intermittent (15 min every 6, 12, and 24 h), or no agitation conditions. The highest cumulative CH4 yield of 339 NmL g-COD−1 was obtained under intermittent agitation once every 12 h, followed by 306 and 304 NmL g-COD−1 under continuous agitation and once per 6 h agitation, respectively. However, lower agitation conditions (once per 24 h and no agitation) showed lower methane yields. Based on the mass balance of chemical oxygen demand, the solubilization efficiency tended to be high under high agitation frequency. Furthermore, the highest acidogenesis and methanogenesis efficiencies were obtained under once per 12 h agitation. The number of microbial cells and the relative abundance of hydrogenotrophic methanogens that work with H2 producing bacteria decreased, likely due to agitation stress. A once per 12 h agitation was sufficient to promote solubilization and avoid agitation stress on microorganisms in the food waste treatment. Moderate intermittent agitation is a promising method for maximizing CH4 recovery and minimizing energy consumption.